In general, farming using seawater can be basically divided into land water tank farming and marine cage farming. The land water tank farming is a method of farming target living things by transferring the living things to a land water tank and artificially regulating a living environment, and the marine cage farming is a method of confining and farming target living things in the wide space of the sea by using a net or the like.
Of these methods, the marine cage farming does not require the exchange of seawater and can farm fishes in large quantities unlike the land water tank farming, and is thus increasing gradually. The marine cage farming is performed by installing a net within a predetermined range in the sea or inland waters, such as waters surrounded by a dam, and farming specific fishes within the net. The marine cage farming is a method of constructing a net or special facility in a deep and wide water area, confining fishes in the net or facility, and farming the fishes therein. The marine cage farming is advantageous in that water can be easily exchanged because water can freely pass through the net inward and outward, oxygen can be smoothly supplied, metabolic wastes discharged during farming do not need to be removed or separated, and also it is considerably easy to farm fishes in large quantities because the quality of water within the cage is not deteriorated even when fishes are farmed in large quantities.
In the marine cage farming, feeding is generally performed in such a manner that a human directly scatters feed on the sea by means of a spraying or dumping method.
However, the marine cage farming is problematic in that a cage farming apparatus is located near the surface of the sea and is thus extremely vulnerable to waves and a typhoon.
Accordingly, the cage farming apparatus is located on the seabed in order to perform marine cage farming regardless of weather conditions. In this case, it is considerably difficult to feed fishes that are being farmed.
Furthermore, the conventional cage farming apparatus is disadvantageous in that it is impossible to freely adjust the depth of seawater at which a cage net is located according to the type of fishes. In particular, a disadvantage arises in that in order to lift a cage net to the surface of the sea when adult fishes are shipped, an operator needs to enter seawater and manually raise the cage net to the surface of the sea, or the cage net needs to be directly raised to the surface of the sea by binding the cage net with a rope and pulling the rope from the outside.